Ecore_X_Image: Add trap for potential missing XImage.

Ecore_X_Image: Add trap for potential missing XImage.
  if Ecore_X_Image-->XImage does not exist, we call
_ecore_x_image_shm_create to create it via shm, BUT that function
can return a NULL XImage if shm is not supported, so we need to check
the return of that, else we are calling XShmPutImage with no XImage.

(NB: This should probably be backported to 1.0...if someone could
handle that please ?)

git-svn-id: http://svn.enlightenment.org/svn/e/trunk/ecore@57130 7cbeb6ba-43b4-40fd-8cce-4c39aea84d33